import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 晓星航
 * Date: 2022-10-15
 * Time: 10:33
 */
public class TestDemo {
    public static int fib(int n){
        if(n == 1 || n == 2){
            return 1;
        } else {
            return fib(n-1)+fib(n-2);
        }
    }
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        System.out.println(fib(n));
    }
}
